Eaton offers Detroit Truetrac gear-type limited-slip

Long the choice of road racers and off roaders, the Truetrac is one of the smartest differentials on the market.

The ability to lay down matching stripes of rubber on the pavement at will is a mandatory muscle car maneuver, but the means of achieving said trick are somewhat varied.

Traditionally, the limited-slip differential has used friction, either through a series of clutch plates or cone-type clutches, to send power to both drive wheels while maintaining the ability to accommodate varying drive-wheel speeds. Eaton developed the clutch-type limited-slip commonly referred to as “posi,” thanks to its Chevrolet-given brand name, Positraction, and continues to manufacture a similar unit today, actually named Posi Limited-Slip Differential. But clutch-type limited-slip units have their flaws, including clutch plates that wear over time, the vibration they can cause, and the sometimes unpredictable engagement of both drive wheels in unfavorable conditions.

As an alternative, Eaton also manufactures the Detroit Truetrac differential, classified as a gear-type limited-slip. The Truetrac uses helical gears to deliver torque to both drive wheels, but only as needed. Under normal conditions, the Truetrac operates as an open differential, but when a difference in wheel torque is encountered, the helical gears begin to engage, delivering more torque to the wheel that is experiencing traction loss.

There are no wear parts, and the Truetrac uses standard lubricants, so no special friction modifiers are required, as with a traditional clutch-type limited-slip differential. Typical driving characteristics are said to be nearly identical to those of an open differential, with no binding or “pushing” in turns. Installation is also straightforward, requiring nothing beyond typical differential R&R. To learn more about how the Truetrac works, what applications it’s available for, and where it can be purchased, go to www.eatonperformance.com.

(This post originally appeared in the July 19, 2007, issue of the Hemmings eWeekly Newsletter.)